My guess is they're using the same strategy as the Snowden leaks - drop a new bombshell at regular intervals through the media, then eventually open source the whole thing. The idea is the maximize the impact of the leaks, not to hide anything (of course, you can disagree about whether it actually does maximize the impact.)
This may be part of their plan, but Snowden used that method for the purpose of hiding things too. He wanted reports about the various software projects being used to be public, he didn't want the software itself to be public.
Vetting data over dumping everything often has benefits.
Not only does it maximize the impact of the leaks, now those defending themselves against the leaks must be very careful not to create a new set of lies that could be disproved by further leaks.
As a hypothetical
FB: we only did that once!
Leaker: in fact you did that many times (shows papers)
Snippets of the source documents are presented in the WSJ Facebook stories that preceded the naming of the whistleblower. They are paywalled here, but you might be able to find the stories on certain archive sites.
Yes. At this point in the world we need not take anyone's word for what a corpus says or does not say. Either the data, query, and processing exist and are documented or they may as well be making things up.
> Notwithstanding the provisions of sections 106 and 106A, the fair use of a copyrighted work, including such use by reproduction in copies or phonorecords or by any other means specified by that section, for purposes such as criticism, comment, news reporting, teaching (including multiple copies for classroom use), scholarship, or research, is not an infringement of copyright.
Fair use is a positive defense though, so you'd have to go through a trial (assumption being Facebook throws enough lawyers at it to make it impossible for a "it's obviously fair use" argument work) to assert it.
A repo need not be in a US or any jurisdiction. If it is important enough to have legislative talking time, it is important enough to be made public for people to make their own decisions about it. By keeping it private this is all hat and no cattle.